1. Field of the Invention
The present invention relates to a method for separating metallic material, such as copper foil, solder, and electronic parts, from waste printed circuit boards, which are recovered from used electrical products or are discarded in manufacturing processes as inferior products or scraps.
Further, the present invention relates to a dry distillation apparatus used for heating and dry distillation of metal-having resin composites and for separation of metal and resin components.
Moreover, the present invention pertains to technology for cleaning-up dry distillation gas from an apparatus used for heating and dry distillation of waste containing combustible organic material into carbonate to reduce weight.
2. Related Art of the Invention
Land disposal in controlled-type landfill sites is presently a general approach to dispose waste printed circuit boards, for example, contained in used electrical products. Because the controlled-type landfill sites are equipped with isolation sheets surrounding the site, harmful substances, such as lead component originating in solder retained on the waste printed circuit boards are prevented from diffusing into the environment even when such harmful components get dissolved in rainwater.
Nevertheless, in the case of potential damage in the isolation sheets, the harmful substances could diffuse into the environment. Therefore, it is still desired to remove the harmful components, such as solder, from the waste printed circuit boards to make them harmless before disposal. Furthermore, since the printed circuit boards and the electronic parts retained thereon contain valuable metals such as copper, it has been desired to efficiently recover and recycle them.
In addition, waste printed circuit boards are also discarded as inferior products or scraps in manufacturing plants, and are presently treated as industrial waste for land disposal described above. It is also desired to efficiently recover and recycle the valuable metals, such as copper, contained in such waste printed circuit boards.
Reflecting such situation, a couple of methods for treating waste printed circuit boards have been proposed. For example, Japanese Laid-open Patent Application No. Hei 6-228667 discloses a method, wherein printed circuit boards retaining electronic parts are pulverized through a coarse and a fine pulverization processes. Then, the pulverized material is separated and recovered using specific gravity separation process into two components: a portion mainly containing metallic material such as copper, and the other portion mainly consists of resin and filler materials.
To pulverize the waste printed circuit boards as described therein, strong pulverizing force is necessary because of toughness of board portion of the waste printed circuit boards. However, the force strong enough to pulverize the printed circuit boards excessively pulverizes solder potion during the pulverization of the board resin component. The excessive pulverization causes a difficulty in the specific gravity separation process to separate the solder component from the board resin component.
Similarly, electronic parts are also excessively pulverized and become difficult to separate from the board resin component. As such, there has been a problem of low recovery efficiency of the metal component, such as solder and electronic parts.
Another prior art method for treating waste printed circuit boards is disclosed in Japanese Laid-open Patent Application No. Hei 8-139446. As described therein, electronic parts soldered on a printed circuit board are removed therefrom by applying an external force to the board while the solder is heated and re-melted.
In this method, however, the external force is exerted also onto the heated and re-melted solder, making the solder to splash into fine drops. This situation causes another difficulty in the recovery of solder. In addition, regarding the electronic parts that are assembled on circuit boards with lead wire""s ends being bent, it is difficult to remove such electronic parts from the circuit boards with this method alone.
On the other hand, a number of heat treatment methods have been proposed for recycling resin material that is contained in used products or manufacturing waste. In one of the methods, the resin material is directly used as fuel in a combustion furnace, and then the heat of combustion of the resin is utilized as energy resource. In an alternative method, the resin material is heated at a high temperature in a low oxygen environment, such as in nitrogen atmosphere, and the generated combustible gas is used as fuel. These methods are called thermal recycle.
In another alternative method, metal-having resin material, which includes printed circuit boards and metallic material such as wiring connectors, is placed into a metal smelting furnace. Valuable metals, such as gold, are recovered and the resin material is used as a substitute for the reducing agent.
In those heat treatment methods using the resin material as a direct fuel, the combustion can be perfect, and hence, its utilization can be efficient, only if the composition of the resin material for treatment is pure. Further, when the material contains metals, the metals remain in the ash, which requires another appropriate treatment.
For printed circuit boards that retain a large amount of solder, a substantial amount of the lead component of the solder retained on the circuit boards can evaporate due to a high temperature in the combustion treatment. Thus, consideration is necessary for proper exhaust gas treatment.
Furthermore, the method for separation of metal and non-metal components using a metal smelting furnace is economically efficient only when a large amount of valuable metals such as gold, is contained in the waste. In other cases of, for example, home appliances, where valuable metals other than copper are scarce, such a method, while technically still possible, has little economical incentive. Therefore, this method has not been generally adopted.
Moreover, a number of methods have been proposed for waste reduction treatment of waste containing combustible organic material, such as garbage discharged from houses or feeding facilities, and offal from food processing plants. Other than incineration treatment and bio-fermentation treatment, there is a method by heating and dry distillation of the waste to reduce its mass. The yielded carbide is used as land improvement stuff.
In the heating and dry distillation method, treatment of dry distillation gas is necessary. Prior art for this includes a method by introducing the gas into a flame combustion furnace to incinerate it at high temperature, and a method of oxidization cleaning of the gas using an oxidizing catalyst.
In the prior art method of incineration of the gas in a flame combustion furnace, a simpler and rather compact apparatus can be used. However, since the composition and amount of the generated dry distillation gas is not constant, the method has a problem that perfect combustion is difficult to maintain, and that unburned components may easily escape.
On the contrary, in the method using an oxidizing catalyst as shown in FIG. 19, dry distillation gas carried out from dry distillation furnace 21B by scavenging fan 22B is introduced through scavenging pipe 23B onto oxidizing catalyst 26B. The temperature of the oxidizing catalyst 26B is maintained by flame burner 25B in gas treatment chamber 24B. A part of combustible component is oxidized by the flame in the vicinity of the flame burner 25B, and the rest part is perfectly cleaned up by the oxidizing catalyst 26B. As such, perfectly treated clean exhaust gas can be exhausted from an exhaust vent 27B.
In this configuration, however, in the case of large variations in the concentration of combustible substances in the dry distillation gas exhausted from dry distillation furnace 21B,stable combustion in the flame burner 25B can deteriorate. Furthermore, when the gas contains a large amount of combustible substances, heat generation in the vicinity of the flame burner 25B becomes excessive, which can overheat oxidizing catalyst 26B.
To stabilize the combustion in the flame burner 25B, excessive air mixing must be avoided. However, an excess of combustible substances causes a shortage of air mixture, which, in turn, suppresses the oxidation reaction on the oxidizing catalyst 26B. As the result, substances not yet reacted, such as odor and carbon monoxide, can escape.
Furthermore, combustion of the flame burner 25B is fixed. Thus, the oxidizing catalyst 26B is kept at around 200-500xc2x0 C. only for a normal amount of combustible gas. When the waste contains salts and halides, production of harmful substances such as dioxins is suppressed in the vicinity of the flame burner 25B because of the high temperature of 800xc2x0 C. or higher. However, since the temperature of the oxidizing catalyst 26B downstream is 200-500xc2x0 C., dioxins can be re-produced here because dioxins are produced at 300-700xc2x0 C.
(1) The invention has been devised considering the above-mentioned problems in the prior art methods for treating waste printed circuit boards, and an object of the invention is to provide a method for treating waste printed circuit boards, wherein solder contamination into the recovered board resin component is suppressed, whereby metal component and board resin component can be efficiently separated.
Accordingly, the present invention has achieved the above object by providing a method for treating waste printed circuit boards, the method comprising the steps of:
heating up for dry-distilling the waste printed circuit boards having copper foil retaining solder in at least a part of the surface, at a temperature of 250xc2x0 C. or higher;
pulverizing the dry-distilled material of said waste printed circuit boards obtained in said heating step; and
separating the pulverized material of said waste printed circuit boards obtained in said pulverizing step, into board resin component and metal component.
(2) An object of the invention is to provide a method for separating metal component from waste printed circuit boards, wherein metal component is efficiently separated from waste printed circuit boards.
Accordingly, another aspect of the present invention is a method for separating metallic material from waste printed circuit boards, the method comprising the steps of:
heating up the waste printed circuit boards having at least metallic material, in an atmosphere avoiding the burning of the printed circuit board portion of said waste printed circuit boards or in an atmosphere avoiding the oxidation of said metallic material, so that the temperature of at least said printed circuit board portion becomes 250xc2x0 C. or higher and lower than 500xc2x0 C.;
pulverizing the substantial printed circuit board portion alone of said waste printed circuit boards heated-up in said heating step into pieces not exceeding a predetermined size; and
separating the pulverized pieces of said substantial printed circuit board portion pulverized in said pulverizing step and said metallic material retained on said waste printed circuit boards, depending on the difference in the sizes of said pulverized pieces and of said metallic material.
(3) An object of the invention is to provide a method for separating electronic parts from waste printed circuit boards, wherein the electronic parts are efficiently separated from the waste printed circuit boards without exerting an external force onto the heated and re-melted solder.
Accordingly, still another aspect of the present invention is a method for separating electronic parts from waste printed circuit boards, the method comprising the steps of:
colliding predetermined particles at the waste printed circuit boards being assembled with electronic parts by particles collision operation;
breaking out the junctions between the board portion of said waste printed circuit boards and said electronic parts, substantially without fracturing of said board portion of said waste printed circuit boards thereby, in said particles collision operation; and
separating said electronic parts from said waste printed circuit boards thereby, in said particles collision operation.
(4) The invention has been devised to resolve problems in the prior art, and an object of the invention is to provide a dry distillation apparatus used for metal-having resin treatment, whereby resin composite containing cheap metal component can be easily separated.
Accordingly, yet another aspect of the present invention is a dry distillation apparatus used for metal-having resin treatment, the apparatus comprising:
a heating furnace for containing the metal-having resin,
a heating means for heating up said heating furnace, and
a scavenging means for sucking and removing the gas within said heating furnace;
wherein said heating means heats up said heating furnace so that the contained said metal-having resin loses its hardness; and
wherein said contained metal-having resin is heated up without burning because at least the surroundings of said contained metal-having resin is oxygen-poor.
(5) The invention has been devised to resolve problems in the prior art, and an object of the invention is to provide a dry distillation apparatus used for waste treatment, wherein stable and perfect combustion is maintained even with variations in the amount of combustible substances in the dry distillation gas generated from a dry distillation furnace, whereby the clean exhaust gas characteristics can be maintained free of harmful substances.
Accordingly, still yet another aspect of the present invention is a dry distillation apparatus used for waste treatment, the apparatus comprising:
a heating furnace for containing and heating up combustible organic waste being put in;
a heating means for heating up the inside of heating up said heating furnace at a predetermined temperature;
a scavenging means for sucking and removing the dry distillation gas generated within said heating furnace;
a gas treating means connect to upstream or downstream of said scavenging means, and for containing an oxidizing catalyst therein;
a fuel and/or air supplying means for supplying fuel and/or air to the inside of said gas treating means connected to upstream of said gas treating means;
a temperature measuring means for measuring the temperature of said oxidizing catalyst; and
a rate controlling means for controlling the supply rate of fuel and/or air supplied by at least said fuel supplying means, in response to the temperature measured by the measuring signal from said temperature measuring means.
The carbide described in this specification generally refers to carbides resulting from board resin component or from printed circuit board portion, but is not restricted to this.